This application relates to a hanger or support for pipes and other elongated members held inside air vents, plenums, ducts or other building conduits for circulating air.
Current construction techniques place ventilation passages and ducts throughout buildings. A number of pipes or conduits may be supported by pipe hangers within these passages or ducts. These pipe hangers have generally been made of metal, mineral products, etc., because in case of fire the pipe support cannot be permitted to burn and generate smoke and noxious fumes. But pipe supports made of such materials can be unnecessarily heavy and expensive, and their installation may be cumbersome and time consuming. Also, because the pipe hangers are of metal or other materials which may be difficult to process, the potential configurations are limited because it is expensive or technically challenging to form detailed shapes or to assemble complex parts. There is thus a need for an improved pipe hanger that can be used inside ventilation ducts and which is easy to manufacture and install.
The various building and mechanical codes in the U.S. (and many other countries) usually place restrictions on the smoke, fire and toxics performance of materials that may be used within building air passageways. In many buildings the spaces between the ceiling and roof, or above a suspended ceiling, or within walls, are often used as an air plenum and form part of the building ventilation system. Thus, said restrictions in the building and mechanical codes can affect not just the installation of ducting and vents, but in some cases can affect everything located, for example between a false ceiling and the roof or the structural ceiling. But the area between the false ceiling and the structural ceiling is also a prime area for the passage of building utilities such as piping and electrical wiring and conduit. Thus, supports for these items within such a building space may also have to conform to the smoke, fire and toxics requirements.
There is a standard, UL-1565, which may be applied to pipe and conduit hangers, etc., but it expressly does not apply to these parts when they are located within air plenums. Nonetheless, various standards and regulations have been applied to varying degrees to the fixtures used in these plenums and ducts. The primary standards often referenced by the various codes and engineers' building specifications for materials used within ducting or plenums are ASTM E-84 and UL-723, which apply to insulation, surface coverings, or other materials in sheet or continuous form. In said standards, the concerns are the generation of smoke and particulates, and the rate of propagation of a flame front. Because these specifications are for sheets of material, their scopes do not encompass small parts like pipe hangers and supports used in air plenums. Thus, the various plastic fittings available for supporting pipes and conduits are not qualified to meet the construction specifications as generally stated, and such use would likely violate the applicable building codes. Further, even if tested in sheet form, the plastic materials commonly used for plastic hangers and supports will not comply with the ASTM E-84 or UL723 standards. As a result, plastic materials are not generally used or permitted in such applications, and fixtures of metal, mineral wool, silicates, etc., are used instead in the plenums, ducts and other air passageways.
Further, the performance rating of a material based on its E-84 testing is typically stated in numerical terms as “xx/yy”, where the value “xx” represents the flame spread rate and “yy” the smoke developed. These values are on a scale where fiber cement has a rating of “0/0” and red oak has a rating of “100/100”. A rating of “0” does not necessarily mean that burning or smoke does not occur, but only reflects a rate or amount that is extremely low. The two ratings are independent, and it is possible to exceed 100 in either rating. Normal wall coverings in buildings are often held to a minimum E-84 rating of 25/450, which allows a high amount of smoke while restricting the allowable burn rate.
For use in air plenums, codes require materials to meet or better an ASTM E-84 rating of 25/50. The plastic materials used for making the pipe hangers and supports that are generally used in other parts of buildings are notorious for generating volumes of toxic smoke and fumes when burned, making the “smoke development” component of the requirements so difficult to meet that plastics support elements are not qualified for use in air plenums. The use of these smoke-generating plastic parts in air plenums is thus effectively barred by building codes. Thus, plastic parts that may be used underneath a house or in the walls of a building, are not qualified for use in air plenums, and are not used. Thus, supports made of polyethylene, polypropylene and nylon are not believed suitable for use in these locations with applicable building codes. Metal and other materials are used instead, with the above-mentioned problems.
Another standard is UL-2043, which normally applies to electrical devices, equipment, speakers, and some other kinds of discrete products that may have combustible components. UL-2043 is directed toward the caloric contribution of the material to the fire, and the amount of smoke generated when burned, but without any specific regard for the actual flammability of the material. This specification thus also does not describe pipe hangers and supports used in air plenums.
While the above-mentioned standards are not written to cover pipe supports and clamps used in air plenums and ducts, overall product compliance with one or more of these specifications is often required on projects. Metal pipe supports and clamps provide the ready solution since no plastic parts qualify for use in the air plenums. But metal parts are heavy, costly, difficult to fabricate and often difficult or time consuming to install or adjust. There is thus a need for improved supports and clamps for use in air plenums.